One of the therapeutic procedures applicable to the present invention is known as percutaneous transluminal coronary angioplasty (PTCA). This procedure can be used, for example, to reduce arterial build-up of cholesterol fats or atherosclerotic plaque. Typically a first guidewire of about 0.038 inches in diameter is steered through the vascular system to the site of therapy. A guiding catheter, for example, can then be advanced over the first guidewire to a point just proximal of the stenosis. The first guidewire is then removed. A balloon catheter on a smaller 0.014 inch diameter second guidewire is advanced within the guiding catheter to a point just proximal of the stenosis. The second guidewire is advanced into the stenosis, followed by the balloon on the distal end of the catheter. The balloon is inflated causing the site of the stenosis to widen. The original catheter can then be withdrawn and a catheter of a different size or another device such as an atherectomy device can be inserted.
Conventional angioplasty balloons fall into high, medium, and low pressure ranges. Low pressure balloons are those that have burst pressures below 6 atmospheres (6.1.times.10.sup.5 Pascals). Medium pressure balloons are those that have burst pressures between 6 and 12 atm (6.1.times.10.sup.5 and 1.2.times.10.sup.6 Pa). High pressure balloons are those that have burst pressures above 12 atm (1.2.times.10.sup.6 Pa). Burst pressure is determined by such factors as wall thickness and tensile strength, for example.
High pressure balloons are desirable because they have the ability to exert more force and crack hard lesions. High pressure balloons are also useful in stent deployment. A biocompatible metal stent props open blocked coronary arteries, keeping them from reclosing after balloon angioplasty. A balloon of appropriate size and pressure is first used to open the lesion. The process is repeated with a stent crimped on a high pressure balloon. The stent is deployed when the balloon is inflated. A high pressure balloon is useful for stent deployment because the stent must be forced against the artery's interior wall so that it will fully expand thereby precluding the ends of the stent from hanging down into the channel encouraging the formation of thrombus.
Many bonding techniques for bonding a balloon to a shaft, as for example, laser welding or heat bonding, require thermally similar materials. Adhesive bonds are useful when bonding materials that have different thermal characteristics. For example, a polyethylene terephthalate (PET) high pressure balloon cannot be heat or laser bonded to a polyethylene (PE) shaft because their melt points are not compatible. For performance reasons a shaft and balloon made of thermally dissimilar materials which cannot be heat or laser bonded to the balloon may be desirable. The advantage of adhesive bonds is a common bonding method for thermally dissimilar materials.
U.S. Pat. No. 4,406,653 to Nunez discloses a method and apparatus for a catheter-balloon assembly wherein the catheter balloon is mounted on the catheter by means of adhesive and, in the preferred mode, an annular internal rib protrusion of the catheter balloon is provided for forming a sharply defined boundary of adhesive thereby aiding in the even and symmetrical inflation of the catheter balloon.
Concentric bonding of coaxial shafts often result in eccentric, inconsistent bonds which can result in bond failure. Some devices use a manufacturing fixture to align the coaxial shafts. External fixtures typically hold the outer diameters of the two shafts and insert one into the other. Shaft diameter, wall thickness and concentricity variation can still result in inconsistent bonds.
Adhesives may wick past the end of the shaft into an unintended lumen. To remedy this some adhesive bonds are lengthened to minimize the chance of the adhesive wicking past the end of the lumen. The presence of an elongated stiff section of adhesive can be a disadvantage with respect to catheter flexibility and trackability. The shorter the bond the easier it is to negotiate a torturous path. What is needed is a balloon bond which minimizes bond length and thereby optimizes flexibility as well as withstands internal pressure of at least 500 psi without leaking or rupturing and which is relatively easy, consistent and reliable to manufacture.